The prior art contains several examples of attempts to utilize the phenomenon of bi-axial orientation in thermal plastic material for the blow molding or various articles. For example, U.S. Pat. Nos. 3,311,684; 3,470,282; 2,919,462, and 3,337,666 provide various blow molding arrangements. Generally, the prior art processes attempt to cool a parison to a uniform orientation temperature, stretch the parison and then blow the stretched parison into a container. Alternatively, other proposals involve the injection molding of a parison, the cooling and the reheating of the injection molded parison, and the blowing of the reheated parison to its final configuration.
Such processes are ill adapted to high production rates, and such processes are not adaptable to conventional, free extrusion blow molding machines now in use in many blow molding operations.
In view of the very substantial advantages residing in blow molding under conditions conducive to bi-axial orientation, there does exist a need for a practical, rapid, efficient blow molding method which is adaptable to the over-all free extrusion blow molding technique. If it were possible, at the same time, to eliminate extraneous flash from the article, e.g. at the neck, handle and bottom portions of a bottle, a long standing need in the art would be satisfied.